Half centuries by Quinton de Kock (60 off 42 balls) and Aiden Markram (70 off 48 balls) followed by a tight spell from pace bowler Lungi Ngidi (3/32) helped South Africa defeat hosts West Indies by 25 runs and clinch the five-match T20I series 3-2 at the Grenada National Stadium here.Defending a total of 168/4, thanks mainly to Markram and De Kock's half centuries, all the visitors' main bowlers made significant strikes to limit the defending World T20 champions to 143/9 despite a flamboyant 52 from opening batsman Evin Lewis on Saturday.Fast bowler Lungi Ngidi, who endured a hammering earlier in the series, bounced back with three wickets, while fellow pacer Kagiso Rabada and seam bowling all-rounder Wiaan Mulder -- playing in place of injured speedster Anrich Nortje -- took two wickets each.However, the most miserly bowling effort came from Tabraiz Shamsi, who conceded just 11 runs in his four overs and claimed the wicket of Chris Gayle, who was dismissed for 11.Earlier, Markram's highest T20I score and another half-century from De Kock set the pace for South Africa. Markram slammed four sixes and three boundaries as he and De Kock put on 128 for the second wicket after Temba Bavuma fell without scoring in the first over bowled by Fidel Edwards.West Indies will now travel to Saint Lucia where they will face Australia in a five-match T20I series at the Daren Sammy Cricket Ground starting July 9.Brief scores: South Africa 168/4 in 20 overs (Q de Kock 60, A Markram 70) beat West Indies 143/9 in 20 overs (E Lewis 52; K Rabada 2/24, L Ngidi 3/32, W Mulder 2/31) by 25 runs.